F 

S47 


KNOPF 

SOME  CINNABAR  DEPOSITS 
IN  WESTERN  NEVADA 


BANCtOIT 

LIBRARY 


University  Library 
University  of  California  •  Berkeley 


DEPARTMENT  OF  THE  INTERIOR 

UNITED  STATES  GEOLOGICAL  SURVEY 

GEORGE  OTIS  SMITH,  DIRECTOR 

BULLETIN  620—1) 


SOME  CINNABAR  DEPOSITS  IN 
WESTERN  NEVAD. 


BY 

ADOLPH  KNOPF 


Contributions  to  economic  geology,  1915,  Part  I 
(Pages  59-68) 

Published  September  14, 1915 


WASHINGTON 

GOVERNMENT     PRINTING     OFFICE 
1915 


DEPARTMENT  OF  THE  INTERIOR 

UNITED  STATES  GEOLOGICAL  SURVEY 

GEORGE  OTIS  SMITH,  DIRECTOR 


620— D 


SOME  CINNABAR  DEPOSITS  IN 
WESTERN  NEVADA 


BY 

ADOLPH  (KNOPF 


15 


Contributions  to  economic  geology,  1915,  Part  I 

(Pages  59-68) 

Published  September  14,  1915 


WASHINGTON 

GOVERNMENT    PRINTING    OFFICE 

1915 


CONTENTS. 


Page. 

Deposits  east  of  Mina 59 

Location  and  history  of  discovery 59 

•General  geologic  features 60 

Features  of  the  prospects 61 

Lost  Steers  group 61 

Keg  and  Barrel  prospect 62 

Cinnabar  King  prospect 62 

Red  Devil  prospect 62 

Deposits  east  of  Beatty 62 

Situation  and  discovery 62 

General  geologic  features 63 

Features  of  the  prospects 65 

Cinnabar  prospect 65 

Early  Bird  prospect 66 

Mammoth  group , 66 

Mammoth  No.  5  claim 67 

Relation  of  the  cinnabar  deposits  to  those  of  the  quicksilver  belt  of  western 

Nevada...  67 


NOTE. — Beginning  with  the  present  volume  the  year  included  in  the  title 
of  the  Survey's  annual  "  Contributions  to  economic  geology  "  will  be  the  year 
of  publication  instead  of  the  year  in  which  the  field  work  reported  was  done. 
This  volume  is  therefore  dated  1915,  and  there  will  be  no  volume  entitled 
*' Contributions  to  economic  geology,  1914."  The  volume  will  be  issued  in 
parts,  as  heretofore,  and  the  last  part  will  include  a  volume  title-page,  table 
of  contents,  and  index  for  the  use  of  those  who  may  wish  to  bind  the  separate 
parts.  A  small  edition  of  the  bound  volume  will  also  be  issued,  but  copies 
can  not  be  supplied  to  those  who  have  received  all  the  parts. 


SOME  CINNABAR  DEPOSITS  IN  WESTERN  NEVADA. 


By  ADOLPH  KNOPF. 


DEPOSITS  EAST  OF  MINA. 

LOCATION"  AND  HISTORY  OF  DISCOVERY. 

A  belt  of  cinnabar  deposits  is  situated  in  the  heart  of  the  Pilot 
Mountains,  in  an  air  line  8  miles  south  of  east  of  Mina,  Esmeralda 
County,  Nev.  The  average  elevation  above  sea  level  here  is  7,300 
feet,  or  about  2,700  feet  above  Mina,  the  local  supply  point,  which  is 
on  the  Southern  Pacific  system.  The  deposits  are  accessible  from 
Mina  by  a  good  wagon  road  of  easy  grade  about  12  miles  long.  The 
area  in  which  the  quicksilver  deposits  occur  supports  sufficient  forest 
growth  to  furnish  wood  for  local  use  as  fuel  and  contains  a  number 
of  springs  that  are  capable  of  furnishing  an  ample  domestic  supply 
of  water.  The  topographic  features  of  the  district  and  its  ap- 
proaches are  shown  on  the  scale  of  1 : 250,000,  or  approximately  4 
miles  to  the  inch,  on  the  United  States  Geological  Survey's  map  of 
the  Tonopah  quadrangle. 

The  discovery  that  drew  attention  to  the  cinnabar  of  Pilot  Moun- 
tains was  made  in  June,  1913.  On  the  day  of  the  discovery  Thomas 
Pepper  and  Charles  Keough  had  been  tracking  two  stray  steers,  when 
near  nightfall  the  trail  led  over  an  old  prospect  in  which  a  face  of 
limestone  traversed  by  small  veinlets  of  red  mineral  was  exposed. 
The  red  mineral  was  recognized  by  Keough  as  cinnabar.  After  find- 
ing the  steers  and  taking  them  to  Mina  the  two  discoverers  returned 
to  Cinnabar  Mountain,  as  the  hill  on  which  they  had  made  the  find 
has  since  been  named,  where  they  spent  10  days  in  careful  search  and 
located  17  claims.  On  June  18  they  went  back  to  Mina  and  made 
known  their  find,  causing  an  intense  excitement,  and  that  afternoon 
almost  every  citizen  of  the  town  left  for  the  site  of  the  discovery  by 
automobile  and  by  other  less  expeditious  conveyances.  A  large  num- 
ber of  claims  were  staked  by  the  first  comers  and  many  more  were 
afterward  staked  by  claimants  from  Tonopah.  Unfortunately  the 
amount  of  exploratory  and  development  work  has  not  been  propor- 
tional to  this  early  enthusiasm. 

The  discovery  was  widely  heralded  as  the  rediscovery  of  the  "  lost 
Hawthorne  quicksilver  mine,"  named  for  Judge  Hawthorne,  in  whose 

98549°— 15 

59 


60  CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,  1915,   PART  I. 

honor  it  is  said  Hawthorne,  the  seat  of  Mineral  County,  is  named. 
According  to  local  report  Judge  Hawthorne  discovered  in  the  seven- 
ties a  rich  quicksilver  deposit,  which  is  believed  to  have  been  situ- 
ated at  the  site  of  the  recent  discoveries.  In  returning  from  the 
mountains,  so  it  is  said,  Hawthorne  lost  his  bearings,  and  although  he 
attempted  annually  to  the  end  of  his  life  to  find  the  "quicksilver 
mine  "  he  remained  unsuccessful.  This  tradition  seems  highly  im- 
probable. The  original  discoverer — who  he  was  is  unknown — had 
done  some  very  substantial  exploratory  work  on  the  prospect.  In  his 
efforts  to  prove  his  find  he  had  blasted  out  a  considerable  mass  of 
solid  limestone,  and  as  further  tokens  of  his  activity  sticks  of  powder, 
fuse,  and  picks  lays  abandoned  at  the  prospect  That  this  energetic 
prospector  lost  his  way  and  was  unable  to  find  the  prospect  at  which 
he  had  labored  is  not  easily  credible.  It  is  more  likely  that  he  aban- 
doned the  prospect  as,  in  his  judgment,  not  sufficiently  valuable. 

The  newcomers  have  found  considerably  richer  deposits  than  the 
unknown  pioneer  did,  and  have  shown  that  the  cinnabar  extends 
along  a  considerable  belt. 

GENERAL  GEOLOGIC  FEATURES. 

Cinnabar  has  been  found  at  a  number  of  places  along  a  belt  that  is 
about  2  miles  long  and  trends  northeastward.  The  main  area  com- 
prises the  hill  known  as  Cinnabar  Mountain.  Limestones  make  up 
the  bulk  of  this  hill,  although  some  dolomitic  graywacke,  composed 
of  angular  and  rounded  quartz  grains  and  of  angular  chert  particles 
embedded  in  a  cement  of  dolomite,  is  interstratified  with  them.  The 
strike  ranges  from  north  to  northeast,  and  the  dip  from  40°  to  70° 
NW.  The  limestones  carry  crinoid  fragments  and  other  obscure 
fossils,  and  are  probably  of  Paleozoic  age.  North  of  Cinnabar 
Mountain  graywacke,  slate,  and  chert  form  the  country  rock.  No 
igneous  rocks,  in  either  dikes  or  flows,  have  been  found  near  the  min- 
eral deposits.  Tertiary  lavas  appear  on  the  north  flank  of  the 
mountains,  but  they  are  4  or  5  miles  from  the  cinnabar  belt. 

The  cinnabar  deposits  on  Cinnabar  Mountain  occur  in  fracture 
zones  in  limestone.  The  limestone  is  traversed  by  thin  veinlets  of 
white  spar,  and  the  cinnabar  is  intergrown  with  the  calcite  or  dolo- 
mite of  the  veinlets  or  occurs  as  a  replacement  of  the  adjoining  wall 
rock.  The  intimate  penetration  of  the  cinnabar  into  the  body  of  the 
limestone  is  locally  a  notable  feature.  Stibnite  is  associated  with  the 
cinnabar  at  one  locality  only;  pyrite  and  marcasite,  characteristic 
associates  of  quicksilver  ores  the  world  over,  do  not  occur  in  the 
district. 

The  geologic  features  of  the  quicksilver  deposits  north  of  Cinnabar 
Mountain  are  somewhat  different.  At  the  Cinnabar  King  prospect 


CINNABAR  DEPOSITS  IN   WESTERN    NEVADA.  61 

the  ore  consists  of  cinnabar  in  a  gangue  of  barite  and  the  deposit  is 
inclosed  in  u  country  rock  of  brecciated  chert.  Farther  north,  at  the 
Ked  Devil  prospect,  the  country  rock  is  "Taywsicke  and  the  cinnabar 
is  disseminated  through  a  siliceous  gangue. 

Although  highly  encouraging  showings  of  cinnabar  ore  have  been 
uncovered  at  a  number  of  places  in  the  district,  the  amount  of  pros- 
pecting so  far  done  is  insufficient  to  prove  that  the  linear  extent  of 
any  deposit,  let  alone  its  persistence  in  depth,  is  great  enough  to 
indicate  its  commercial  importance.  The  geologic  features  of  the 
deposits  appear  to  be  favorable  to  persistence  of  the  ore  in  depth  of 
the  grade  and  character  of  that  at  the  outcrop,  for  the  mineralization 
is  obviously  of  a  kind  in  which  the  deposition  of  the  cinnabar  was  not 
dependent  on  immediate  proximity  to  the  surface,  as  it  is,  for  exam- 
ple, in  quicksilver  deposits  that  are  formed  at  the  vents  of  hot  springs. 

The  prospects  at  which  the  most  exploratory  work  has  been  under- 
taken will  now  be  described. 

FEATURES   OF   THE   PROSPECTS. 

Lost  Steers  group. — The  Lost  Steers  group  consists  of  11  claims 
owned  by  Thomas  Pepper  and  Charles  Keough.  The  most  develop- 
ment work  so  far  accomplished  in  the  district  has  been  done  on  the' 
claims  of  this  group.  At  the  lowrest  workings  a  tunnel  about  75  feet 
long  has  been  driven,  but  its  course  is  such  that  it  fails  to  undercut 
the  ore  exposed  at  the  surface. 

A  zone  several  hundred  yards  long,  extending  from  the  mouth  of 
the  tunnel  on  the  north  to  the  open  cut  made  on  the  summit  of  the 
mountain  by  the  pioneer  prospector,  carries  cinnabar  at  intervals. 
The  geologic  features  are  essentially  similar  at  the  different  ex- 
posures. The  country  rock  is  a  fine-grained  dark  limestone,  which  is 
cut  by  veinlets  of  white  spar  and  is  sporadically  impregnated  with 
crystallized  cinnabar.  Locally  the  cinnabar  without  any  associated 
gangue  mineral  replaces  the  limestone,  and  such  occurrences  consti- 
tute a  very  high  grade  of  ore.  At  one  locality  some  bunches  of  stib- 
nite  have  been  found,  but  elsewhere  cinnabar  is  the  only  sulphide 
mineral  in  the  deposits.  At  the  different  occurrences  of  cinnabar 
along  the  zone  there  is  evidence  that  fracturing  of  the  limestone  was 
of  importance  in  the  genesis  of  the  ore.  For  example,  at  the  shaft, 
which  is  about  6  feet  deep,  two  fairly  well  defined  walls,  52  inches 
apart,  can  be  seen.  They  trend  X.  40°  W.,  and  the  footwall.  which 
is  the  better  defined  of  the  two,  dips  70°  SW. 

The  cinnabar  shown  in  the  open  cut  on  the  Lost  Steers  claim  No.  1 
occurs  in  a  different  fracture  system  from  the  one  just  described. 
The  deposit  on  this  claim  lies  on  the  east  side  of  the  summit  of  Cin- 
nabar Mountain.  The  limestone  country  rock  strikes  north  and  dips 


62  CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,  1915,  PART  I. 

40°  W.  An  excellently  denned  wall,  striking  north  45°  W.  and 
dipping  70°  NE.,  forms  the  footwall  of  the  deposit.  The  lime- 
stone lying  upon  this  wall  is  reticulated  with  sparry  veinlets  of  cal- 
cite  carrying  cinnabar,  which  occurs  locally  in  considerable  masses 
characterized  by  splendent  cleavage  faces.  The  system  of  cinnabar- 
bearing  calcite  veinlets  extends  at  least  6  feet  from  the  footwall. 
Rarely  streaks  of  ore  make  out  into  the  footwall  zone. 

Keg  and  Barrel  prospect. — An  open  cut  at  this  prospect  shows  a 
well-defined  wall  striking  X.  30°  E.  and  dipping  70°  W.  The  coun- 
try rock — a  fine-grained  dark  dolomite — under  this  wall  is  netted 
with  white  veinlets  of  dolomite  averaging  a  fourth  of  an  inch  in 
thickness.  Coarsely  crystallized  cinnabar  occurs  in  the  veinlets  to 
some  extent,  but  mainly  as  a  replacement  of  the  adjoining  country 
rock. 

Cinnabar  King  prospect. — The  Cinnabar  King  prospect  is  a  short 
distance  north  of  Cinnabar  Mountain.  The  exploration  work  so  far 
done  consists  of  a  small  pit,  which  affords  but  inadequate  information 
as  to  the  nature  and  extent  of  the  occurrence  of  the  ore.  This  ex- 
poses the  face  of  a  body  of  ore,  about  4  feet  thick,  dipping  20°  N., 
as  far  as  can  be  determined  by  the  small  developments,  The  ore 
consists  of  barite  carrying  disseminated  cinnabar  and  averages  per- 
haps 4  per  cent  of  quicksilver.  The  general  country  rock,  unlike  that 
of  Cinnabar  Mountain,  is  a  highly  fractured  chert. 

Red  Devil  prospect. — This  prospect,  owned  by  A.  C.  Roach,  Eugene 
Grutt,  and  A.  Drew,  is  about  1|  miles  north  of  Cinnabar  Mountain. 
A  shallow  open  cut  discloses  a  body  of  good  grade  ore,  30  inches  thick, 
apparently  dipping  at  a  low  angle  to  the  west.  The  ore  consists  of 
ocherous  cinnabar  in  a  fine-grained  siliceous  gangue.  The  country 
rock  is  a  coarse  graywacke  made  up  largely  of  flat  angular  fragments 
of  black  slate. 

DEPOSITS  EAST  OF  BEATTY. 

SITUATION  AND  DISCOVERY. 

A  number  of  quicksilver  deposits  are  situated  G  miles  east  of 
Beatty,  Nye  County,  Nev.,  the  junction  of  the  Tonopah  &  Tide- 
water and  the  Las  Vegas  &  Tonopah  railroads.  The  quicksilver- 
bearing  area  lies  in  the  Fluorine  mining  district.  The  prospects  fall 
into  two  groups,  one  on  the  east  slope  of  Bare  Mountain  and  the  other 
on  the  northern  end  of  Yucca  Mountain,  3  miles  northeast.  Locally 
the  part  of  the  Bare  Mountain  group  of  hills  on  which  the  quicksilver 
prospects  occur  is  known  as  Meiklejohn  Mountain.  The  area  is 
readily  accessible  by  roads  of  easy  grade.  The  topographic  features 
of  the  area  are  shown  on  a  scale  of  1:250,000  on  the  United  States 
Geological  Survey's  map  of  the  Furnace  Creek  quadrangle. 


CINNABAR   DEPOSITS   IN    WESTERN    NEVADA.  6$ 

At  the  time  of  the  principal  activity  at  Rhyolite,  in  the  years  im- 
mediately following  1905,  prospectors  spread  out  into  the  neighbor- 
ing territory.  The  east  flank  of  Bare  Mountain  was  the  scene  of  con- 
siderable activity  in  the  search  for  gold,  and  on  the  Grochon  claim 
high-grade  gold  ore,  said  to  carry  tellurides,  was  found.  This  ore 
occurs  in  a  small  irregular  vein,  of  fine-grained  quartz  showing  no 
metalliferous  constituents,  but  the  lowest  assays  are  reported  to  have 
run  as  high  as  $84  a  ton  in  gold.  This  created  much  excitement  at  the 
time,  and  the  camp  that  sprang  up  here  was  named  "Telluride." 
Quicksilver  ore  was  discovered  in  place  on  the  east  flank  of  Bare 
Mountain  by  J.  B.  Kiernan  and  A.  A.  Turner  in  1908,  although  indi- 
cations of  cinnabar  had  been  found  somewhat  earlier.  Attention 
having  thus  been  drawn  to  the  occurrence  of  quicksilver,  it  was  soon 
shown  to  have  a  considerably  wider  distribution.  In  1912  a  10- ton 
Scott  furnace  was  built  in  Gold  Gulch  by  the  Telluride  Consolidated 
Quicksilver  Mining  Corporation.  It  is  on  the  northeast  slope  of 
"  Financier  Hill,"  as  it  is  locally  known,  one  of  the  low  hills  at  the 
northern  end  of  Yucca  Mountain,  where  this  range  merges  into  the 
hills  of  the  Bare  Mountain  group.  A  tunnel  some  1,100  feet  long, 
starting  near  the  furnace,  was  driven  under  this  hill,  which,  it  is  said, 
was  thought  to  contain  $22,000,000  worth  of  ore,  but  no  ore  was  found. 
The  company  then  leased  a  number  of  properties  on  Meiklejohn 
Mountain  and  operated  them,  hauling  the  ore  by  teams  to  the  fur- 
nace, a  distance  of  4  miles.  In  August,  1914,  the  company  became 
involved  in  financial  difficulties,  its  property  was  attached,  and  all 
work  was  suspended.'  At  other  places  in  the  district  a  small  amount 
of  prospecting  was  in  progress  during  1914. 

GENERAL  GEOLOGIC  FEATURES.1 

The  general  country  rock  of  the  quicksilver-bearing  area  on  the 
east  slope  of  Bare  Mountain  is  a  fine-grained  gray  dolomite.  It  is 
rather  massively  bedded  and  has  undergone  considerable  disturbance, 
so  that  its  stratification  is  not  readily  discernible,  but  south  of  Tellur- 
ide camp  the  beds  dip  20°  N.  The  age  of  the  rocks,  as  determined 
from  fossils  embedded  in  a  block  of  dolomite  kindly  sent  to  the  Geo- 
logical Survey  by  Mr.  A.  A.  Turner,  is  Silurian.  Dr.  Edwin  Kirk 
reports  that  the  fossils  include  the  species  named  below : 

Thecia  major.  Syringopora  sp. 

Coenites  verticillata.  Conchidiuni  (2  species). 

Favosites  cristatus.  Pisocrinus  sp. 

1  The  broader  features  of  the  geology  and  their  relation  to  those  of  the  surrounding  ter- 
ritory have  been  discussed  by  S.  H.  Ball  in  A  geologic  reconnaissance  in  southwestern 
Nevada  and  eastern  California  :  U.  S.-  Geol.  Survey  Bull.  308,  1907. 


64  CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,   1915,   PART   I. 

Dr.  Kirk  adds : 

This  collection  is  of  considerable  interest,  as  it  fixes  rather  definitely  the 
age  of  the  widespread  Silurian  fauna  of  the  Western  States.  The  beds  cor- 
relate approximately  with  the  Fusselman  limestone  of  the  El  Paso  region  and 
the  Laketown  dolomite  of  Utah..  On  the  evidence  of  the  fossils  in  the  present 
lot  it  is  safe  to  place  the  fauna  near  the  top  of  the  Niagaran. 

At  the  base  of  Bare  Mountain  a  narrow  belt  of  quartzite  appears 
between  the  dolomite  and  the  upper  edge  of  the  piedmont  alluvial 
slope. 

The  rocks  are  cut  by  a  number  of  porphyry  dikes.  Large  pheno- 
crysts  of  quartz  are  prominent  constituents  of  the  rock  of  these 
dikes.  In  fact,  after  the  dike  rock  has  become  scarcely  recognizable 
from  decomposition,  as  it  commonly  does,  only  the  quartz  crystals 
are  distinguishable  and  serve  to  reveal  the  identity  of  the  altered 
rock.  Feldspar  and  biotite  also  appear  among  the  phenocrysts.  Ex- 
amination under  the  microscope  of  some  of  the  better  preserved  mate- 
rial from  the  Columbia  dike — which,  however,  has  been  altered  by 
the  development  of  pyrite,  dolomite,  and  chlorite — suggests  that  it 
is  a  quartz  diorite  porphyry.  The  dikes  are  possibly  related  in  origin 
to  the  igneous  masses  represented  by  the  pegmatites  that  are  common 
in  the  northern  part  of  the  range.1 

The  quicksilver-bearing  area  north  of  Meiklejohn  Mountain  is 
underlain  by  a  gently  dipping  succession  of  rhyolite  flows  and  tuffs. 
They  are  part  of  the  rhyolite  series  exposed  in  the  Bullfrog  district, 
where  they  attain  a  thickness  of  more  than  6,000  feet.2  They  are 
thought  by  Ball  to  be  of  early  Miocene  age. 

The  quicksilver  deposits  inclosed  in  the  dolomite  consist  of  masses 
of  opal  or  of  cryptocrystalline  silica  carrying  cinnabar;  those  in- 
closed in  the  rhyolites  consist  of  masses  of  opal  and  alunite  carrying 
cinnabar.  The  deposits  contain  no  other  metallic  sulphides,  such  as 
pyrite,  marcasite,  or  stibnite,  which  are  generally  associated  with 
quicksilver  ores.  The  gangue  commonly  contains  large  bodies,  in 
places  as  much  as  10  feet  thick,  consisting  of  a  soft  white  sub- 
stance, which,  as  shown  by  an  analysis  made  by  R.  K.  Bailey  in  the 
laboratory  of  the  Geological  Survey,  is  a  nearly  pure  hydrated  silica, 
namely,  silica,  90.46  per  cent;  water  (loss  on  ignition),  5.38  per  cent. 
This  substance  is  accordingly  a  pulverulent  variety  of  opal.  Al- 
though opal  of  the  hard,  massive  kind  is  the  predominant  gangue 
mineral  of  the  deposits,  various  forms  of  cryptocrystalline  silica, 
comprising  chalcedony  and  exceedingly  fine  grained  quartz  also 
occur.  Locally  all  three  of  these  forms  of  silica  are  intimately  asso- 
ciated in  the  same  deposit.  The  only  departure  from  the  prevailing 

i  Ball,  S.  H.,  op.  cit.,  pp.   155-156. 

-  Ran  some,  F.  L.,  Emmons,  W.  H.,  and  Garrey,  G.^H.,  Geology  and  ore  deposits  of  the 
Bullfrog  district,  Nevada:  U.  S.  Geol.  Survey  Bull.  407,  p.  31,  1910. 


CINNABAR  DEPOSITS   IN   WESTERN    NEVADA.  65 

simple  mineralogy  of  the  district  is  that  shown  by  the  deposit  cut  in 
the  Banner  tunnel.  This  consists  of  a  chimney,  a  few  feet  in  di;»- 
meter,  of  shattered  dolomite  cemented  by  coarsely  crystalline  calcite 
and  barite  and  carrying  a  small  amount  of  cinnabar. 

The  quicksilver  ore  occurs  in  irregular,  erratic  shoots  in  the 
siliceous  masses.  In  the  dolomite  the  bodies  of  opal  and  crypto- 
crystalline  silica  are  commonly  small  and  are  erratically  distributed ; 
in  the  rhyolite,  however,  the  opalized  belts  extend  for  a  thousand 
feet  or  more  and  attain  widths  of  as  much  as  200  feet.  In  the 
opalized  rhyolite  the  quartz  phenocrysts  only  have  remained  intact; 
the  sanidine  phenocrysts  have  been  transformed  largely  into  alunite, 
the  hydrous  sulphate  of  aluminum  and  potassium,  and  the  rest  of 
the  rock  has  been  converted  into  opal,  or  into  pulverulent  hydrated 
silica,  with  which  is  associated  a  notable  amount  of  alunite.  The 
opalized  condition  of  the  rhyolites  is  readily  recognizable  by  the 
unaided  eye,  but  the  presence  of  the  alunite  becomes  manifest  only 
under  the  microscope.  The  optical  determination  of  the  alunite  was 
verified  chemically  by  its  sulphate  reaction.  In  spite  of  the  pro- 
found alteration  of  the  rhyolite,  it  retains  with  remarkable  distinct- 
ness the  normal  appearance  of  an  igneous  rock. 

This  occurrence  of  alunite  with  cinnabar  is  of  scientific  interest, 
for  this  mineral  has  not  heretofore  been  recorded  in  association  with 
quicksilver  ores.  It  has,  however,  been  described  as  occurring  in 
considerable  quantity  in  the  sulphur  deposits  resulting  from  the 
solfataric  alteration  of  rhyolite  tuffs  at  Rabbit  Hole  Springs,  Xev., 
and  these  deposits  contain  traces  of  cinnabar.1  At  Goldfield,  which 
is  65  miles  northwest  of  the  quicksilver  deposits  near  Beatty,  alunite 
is  an  abundant  constituent  of  the  gold  ores.  A  quicksilver  deposit 
occurs  at  Goldfield;  but,  singularly  enough,  this  deposit,  believed 
by  Ransome2  to  be  a  result  of  the  same  mineralization  that  produced 
the  gold  lodes,  or  one  closely  preceding  or  following  it,  does  not 
contain  alunite,  the  mineral  so  characteristic  of  the  district. 

The  cinnabar  in  the  deposits  east  of  Beatty  is  not  present  in  quan- 
tities proportional  to  the  amount  of  opalization  and  alunization,  how- 
ever, but  occurs  sporadically  throughout  the  belts  of  altered  rhyo- 
lite. A  more  thorough  prospecting  of  these  belts  than  has  yet  been 
attempted  appears  advisable. 

FEATURES  OF  THE  PROSPECTS. 

Cinnabar  prospect. — The  Cinnabar  prospect,  owned  by  the  Denver- 
Bullfrog  Mining  Co.,  is  on  the  southeast  side  of  Meiklejohn  Moun- 

1  Adams,  G.  I.,  The  Rabbit  Hole  sulphur  mines,  near  Humboldt  House,  Nevada  :  U.  S. 
Geol.  Survey  Bull.  225,  pp.  499-500,  1904. 

2  Ransome,  F.  L.,  Geology  and  ore  deposits  of  Goldfield,  Nevada  :  U.   S.  Geol.  Survey 
Prof.  Paper  66,  pp.  113,  174,  1909. 


66  CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,  1915,   PART  I. 

tain.  The  principal  development  work  is  a  tunnel  200  feet  long,  which 
intersects  the  cinnabar  deposit  at  a  depth  of  100  feet.  From  the 
portal  of  the  tunnel  a  gravity  tram  extends  to  the  base  of  the  moun- 
tain, 600  feet  below.  A  D  retort,  with  a  capacity  of  800  pounds  in 
12  hours,  has  been  installed  on  the  property,  and  some  flasks  of 
quicksilver  have  been  produced.  The  ore  body  has  been  worked 
mainly,  however,  under  lease  to  the  Telluride  Consolidated  Quick- 
silver Corporation,  wrhich  hauled  the  ore  to  their  furnace  on  Gold 
Gulch. 

The  country  rock  inclosing  the  ore  body  is  a  hard,  fine-grained 
arenaceous  dolomite.  At  the  outcrop  the  cinnabar-bearing  deposit 
has  a  length  of  about  125  feet;  in  the  tunnel  below,  about  70  feet. 
Opal  is  the  principal  gangue  mineral.  A  great  mass  of  opal,  gen- 
erally milk-white  in  color  and  more  or  less  porous  and  cavernous  in 
structure,  is  exposed  in  the  tunnel.  In  this  opal  there  are  large 
pockets  filled  with  soft,  white  hydrated  silica,  an  analysis  of  which  is 
given  on  page  64.  Some  of  these  masses  of  silica  are  6  to  10  feet 
thick.  Chalcedony  forms  an  insignificant  proportion  of  the  opal 
mass.  Locally  the  opal  containing  cinnabar  is  of  gem  quality,  and 
some  of  this  material  has  been  polished  and  placed  on  the  market. 

The  cinnabar  is  either  inclosed  in  the  opal  as  massive  mineral  or 
is  so  very  finely  disseminated  through  the  opal  as  to  give  it  a  blood- 
red  color.  Some  of  the  high-grade  cinnabar  ore,  as  determined  under 
the  microscope,  proves  to  be  a  replacement  of  arenaceous  dolomite. 
Some  of  the  replaced  rock,  in  fact,  contains  sufficient  detrital  quartz 
to  be  a  dolomitic  sandstone.  The  quartz  grains,  many  of  which  are 
perfectly  rounded,  have  remained  intact,  but  the  dolomite  cement  in 
which  they  were  embedded  has  been  replaced  by  chalcedony,  opal, 
and  cinnabar.  Only  rarely  has  a  little  quartz  been  deposited  in 
optical  continuity  with  the  detrital  quartz  grains. 

Early  Bird  prospect. — The  Early  Bird  prospect,  which  is  owned  by 
the  Telluride  Consolidated  Quicksilver  Mining  Corporation,  is  on 
the  north  flank  of  Meiklejohn  Mountain,  near  its  base.  A  large  reef 
of  cryptocrystalline  silica  projects  prominently  above  the  inclosing 
limestone ;  it  is  several  hundred  feet  long  and  at  its  maximum  is  over 
100  feet  wide.  It  contained  a  short,  narrow  shoot  of  high-grade  cin- 
nabar ore,  which  has  been  largely  removed  through  an  adit  cutting 
the  reef  at  a  shallow  depth. 

Mammoth  group. — The  claims  of  the  Mammoth  group  (Nos.  1, 
2,  and  3),  owned  by  the  Telluride  Consolidated  Quicksilver  Mining 
Corporation,  extend  along  a  belt  of  opalized  and  alunitized  rhyolite 
trending  N.  30°  W.  At  its  south  end  this  belt  is  several  hundred 
feet  wide.  The  main  work  has  been  done  on  Mammoth  No.  2,  where 
a,  tunnel  50  feet  long  was  driven  into  a  porous,  cavernous  siliceous 
mass,  evidently  representing  a  place  of  more  intense  alteration  of  the 


CINNABAR  DEPOSITS  IN   WESTERN   NEVADA.  67 

rhyolite.  A  number  of  open  cuts  and  shallow  shafts  have  been  ex- 
cavated at  other  points,  but  no  extensive  bodies  of  quicksilver  ore 
have  so  far  been  found. 

Mammoth  No  5  claim. — The  Mammoth  No.  5,  owned  by  J.  F. 
Grant  and  associates,  is  situated  on  another  belt  of  silicified  rhyolite, 
which  lies  somewhat  west  of  the  Mammoth  group  of  the  Telluride 
Consolidated  Co.  It  is  said  to  be  traceable  for  more  than  1,000  feet, 
but  has  been  prospected  only  by  a  few  shallow  open  cuts.  The  ore 
masses  consist  of  a  soft  white  material — hydrous  silica  mixed  with 
opal  and  alunite — carrying  finely  disseminated  cinnabar.  This  is 
traversed  by  irregular  veins  and  masses  of  white  opal  and  chal- 
cedony. The  ore  material  at  the  main  prospect  trench  is  the  product 
of  the  transformation  of  porphyritic  obsidian  by  siliceous  cinnabar- 
bearing  solutions. 

In  places  along  the  belt  of  silicified  rhyolite  outcrops  of  chalcedony 
and  opal  as  much  as  50  feet  wide  appear.  Although  the  best  ore  so 
far  found  occurs  in  the  soft,  pulverulent  material,  some  cinnabar  is 
locally  inclosed  in  the  hard  siliceous  reefs. 

RELATION   OF   THE  CINNABAR  DEPOSITS  TO  THOSE  OF 
THE  QUICKSILVER  BELT  OF  WESTERN  NEVADA. 

The  existence  of  a  quicksilver-bearing  belt  in  western  Nevada,  in 
Humboldt,  Esmeralda,  and  Nye  counties,  has  long  been  recognized. 
The  information  concerning  the  cinnabar  deposits  of  this  belt  has 
recently  been  assembled  by  McCaskey,1  who  contributes  also -a  de- 
scription of  the  ore  bodies  at  lone,  in  Nye  County,  the  locality  from 
which  the  principal  production  has  so  far  been  derived.  The  deposits 
east  of  Beatty  described  in  the  present  report  extend  the  quicksilver 
belt  considerably  farther  south. 

The  general  tendency  of  those  who  have  described  the  deposits  of 
this  belt  has  been  to  regard  them  as  genetically  connected  with  the 
Tertiary  and  Quaternary  volcanism  of  the  province.  The  phenomena 
observable  at  Steamboat  Springs  support  this  conjecture.  The  hot 
waters  issuing  from  these  springs  deposit  a  siliceous  sinter  which 
contains  cinnabar  and  amorphous  red  antimony  sulphide,  together 
with  lesser  quantities  of  other  metallic  sulphides.  According  to 
Becker2  the  deposits  have  formed  close  to  the  edge  of  a  basalt  flow 
and  probably  result  from  the  volcanic  action  of  which  the  lava 
eruption  was  one  manifestation.  He  believes  that  the  water  issuing 
from  the  springs  comes  from  the  Sierra  Nevada;  that  it  descends 
to  great  depths,  where  it  becomes  heated  by  contact  with  subterranean 
masses  of  hot  basalt,  and  ascends  along  the  fissures  by  which  the  lava 

1  McCaskey,   H.   D.,  Quicksilver :  U.    S.   Geol.    Survey   Mineral   Resources,    1911,    pt.    1, 
pp.  906-909,  1912. 

2  Becker,   G.  F.,  Geology  of  the  quicksilver  deposits  of  the  Pacific  slope :  U.   S.   Geol. 
Survey  Mon.  13,  pp.  338-350,  1888. 


68  CONTRIBUTIONS   TO   ECONOMIC   GEOLOGY,   1915,  PAET  I. 

reached  the  surface.  Concerning  the  genesis  of  the  other  quicksilver 
deposits  of  the  western  Nevada  belt,  opinions  have  been  less  precisely 
formulated,  although,  as  already  mentioned,  these  deposits  also  are 
regarded  as  of  "  volcanic  origin,"  but  probably  this  term  is  now  used 
in  a  sense  different  from  that  which  Becker  had  in  mind. 

It  is  difficult,  however,  to  show  that  some  of  the  deposits  are  re- 
lated to  the  Tertiary  volcanism  of  the  province.  Ransome,1  in  fact, 
is  inclined  to  regard  the  quicksilver  deposits  of  the  Humboldt  Range 
as  of  early  Cretaceous  age.  The  same  difficulty  inheres  in  any 
tittempt  to  connect  the  cinnabar  deposits  east  of  Mina  with  Tertiary 
eruptive  activity.  On  the  other  hand,  it  is  interesting  to  note  that  a 
quicksilver  deposit,  clearly  of  Tertiary  age,  occurs  in  the  volcanic 
rocks  at  Goldfield,  which  is  midway  between  Mina  and  Beatty.2 
The  deposits  near  Beatty  are  rather  obviously  associated  with  the 
Tertiary  volcanism  of  that  region.  This  association  raises  an  impor- 
tant problem,  for  in  the  Bullfrog  district,  a  few  miles  west  of  Beatty, 
the  gold  deposits,  according  to  Ransome,3  are  genetically  connected 
with  this  same  general  outburst  of  volcanism,  though  it  was  not  found 
possible  to  link  the  ore  deposition  with  any  particular  one  of  the 
many  magmas  that  solidified  as  the  lavas  now  exposed  in  the  district. 
Among  the  most  noteworthy  facts  shown  by  the  study  of  the  district 
is  the  remarkably  feeble  chemical  alteration  of  the  wall  rocks  of  the 
ore  bodies;  and  it  was  therefore  concluded  that  the  vein-forming 
solutions  were  dilute,  cool,  and  under  no  heavy  pressure.  Now  the 
notable  feature  of  the  quicksilver  deposits  in  the  rhyolites  east  of 
Beatty  is  the  intense  alteration  of  the  rocks — their  complete  silicifi- 
cation  and  alunitization  in  belts  hundreds  of  yards  long  and  as  much 
as  200  feet  wide.  This  profound  alteration  points  to  the  conclusion 
that  the  quicksilver-bearing  solutions  were  under  physical  and 
chemical  conditions  quite  different  from  those  that  prevailed  during 
the  deposition  of  the  auriferous  ores.  From  these  considerations  and 
from  others  arising  from  a  review  of  the  literature  of  the  subject  it 
appears  that  the  genetic  relation  of  the  cinnabar  deposits  to  the  many 
gold  deposits  scattered  through  the  western  Nevada  quicksilver  belt 
constitutes  an  interesting  problem  for  future  research. 

1  Ransome,  F.  L.,  Notes  on  some  mining  districts  in  Humboldt  County,  Nev. :  TJ.  S.  Geol. 
Survey  Bull.  414,  pp.  46,  71,  1909. 

2  Ransome,  F.  L.,  Geology  and  ore  deposits  of  Goldfield,  Nev. :  TJ.  S.  Geol.  Survey  Prof. 
Paper  66,  p.  113,  1909. 

3  Ransome,  F.  L.,  Geology  and  ore  deposits  of  the  Bullfrog  district,  Nevada  :  TJ.  S.  Geol. 
Survey  Bull.  407,  p.  103,  1910. 

O 


